BAGHDAD – Suicide attackers struck near a Shiite mosque north of Baghdad and a checkpoint west of the capital on Monday as bombings killed at least 17 people nationwide. The violence was concentrated in former Sunni insurgent strongholds that have seen a sharp decline in violence after local tribal leaders turned against al-Qaida in Iraq. Despite the relative calm, a series of deadly bombings have raised concerns about a resurgence of violence as the U.S. military scales back its presence, with a full withdrawal planned by the end of 2011. The attacks  which mainly targeted checkpoints and Iraqi policemen  also highlighted the weaknesses in the Iraqi security forces, which are struggling to prove they are ready to take over from the Americans. The deadliest attack was a suicide car bomber who struck a line of vehicles waiting to be inspected before crossing a bridge near the Anbar provincial capital of Ramadi, police said. The blast set half a dozen other vehicles ablaze, killing three policemen and five civilians and wounding 16 other people, according to police and hospital officials, who spoke on condition of anonymity because they were not allowed to release the information. A farmer riding in a pickup truck not far behind the attacker's car ran toward the scene, where he described seeing a child who had been blown by the blast onto the roof of a car. "I tried to approach him to see whether he was alive or dead, but the police started to open fire in all directions and we had to run away," he said. Iraqi police frequently fire into the air at bombing sites to disperse the crowd and scare away other potential attackers. Ramadi, 70 miles 115 kilometers west of Baghdad, was once one of the most dangerous cities in Iraq before the U.S.-funded Sunni revolt against al-Qaida more than two years ago. Hours later, a suicide bomber wearing a police uniform blew himself up at the gate of a Shiite mosque in Baqouba, 35 miles 60 kilometers northeast of Baghdad, killing at least five people  three policemen and two worshippers  and wounding 20, according to police and hospital officials. Maj. Ghalib al-Karkhi of the provincial police said the bomber was forced to detonate his explosives prematurely after guards stopped him and asked for his ID card. The mainly Sunni city of Baqouba also has been hit by several bombings despite an overall decline in violence. In Baghdad on Monday, a bomb destroyed a police car, killing one officer and two civilians and wounding eight, police said. Another bomb killed a driver as he approached a military checkpoint in the Sadr City district. Prime Minister Nouri al-Maliki has sought to reassure Iraqis that the U.S.-trained security forces are capable of taking over from American troops who have withdrawn from the country's cities. Recent bombings, especially an Aug. 19 attack on government ministries in Baghdad that killed about 100 people, have shaken people's confidence at a crucial time, just months before Iraqis go to the polls in January to choose a new parliament. Iraq's rampant corruption has also become a key election issue. Corruption watchdog Transparency International rated Iraq in 2008 as the third most corrupt country in the world after Somalia and Myanmar. The Iraqi government had long played down the issue before announcing a crackdown this year. A judge said Monday that it issued two new arrest warrants. A senior Finance Ministry official in charge of the auditing department is accused of wasting public funds, judge Arif Shahin said. Authorities are also seeking Iraq's ambassador to Jordan. He is accused of sheltering a fellow Saddam Hussein-era diplomat who is wanted in the 1994 assassination of an Iraqi dissident in Beirut, said another judge at the court, Ali al-Rubaie. Associated Press Writers Sameer N. Yacoub and Hamid Ahmed in Baghdad and Jamal Halaby in Amman, Jordan, contributed to this report.